1. Field of the Invention
This invention relates to a zoom lenses and more particularly to high magnification range zoom lenses suited to still cameras.
2. Description of the Prior Art
Examples of the typical prior art zoom lenses include the so-called two-component zoom lens, which includes two components of negative and positive powers, and the so-called four-component zoom lens, which includes from components having, from front to rear, a focusing portion, a variator portion, a compensator portion and a relay portion.
Where a zoom lens of extended zooming or image magnification range is desired, the use of the two-component zoom lens makes it difficult to correct all aberrations, particularly spherical aberration for the telephoto positions. Use of the four-components zoom lens, on the other hand, necessitates a marked strengthening of the refractive power of the zoom portion. Accordingly, it is difficult to correct all aberrations in a balanced system. Moreover, the longitudinal length of the entire system and the diameter of the front component must be increased. Thus, the prior art two and four component zoom lenses were not suited for the purpose.
Many new zoom lenses have been proposed in recent years, one of which uses at least three components to share the magnification power varying effect to obtain a higher magnification range.